Color-changing devices which have been disclosed so far as devices for causing toys employing a photochromic compound to change in color include: an optically color-changing device in a weapon form which irradiates ultraviolet rays upon a photochromic toy; an optically color-changing device in display form which includes an ultraviolet light-emitting diode set in a vessel and which causes a photochromic toy placed on the vessel to change in color (see, for example, patent document 1); an optically color-changing device which includes an ultraviolet light-emitting diode set in a vessel and which causes a photochromic toy housed in the vessel to change in color (see, for example, patent document 2); a color-changing device which irradiates ultraviolet rays while moving, upon a photochromic toy to cause color change (see, for example, patent document 3); and an optically color-changing device in writing utensil form which irradiates ultraviolet rays and is capable of forming traces of handwriting on a photochromic writing board (see, for example, patent document 4).
Those optically color-changing devices can cause photochromic toys to change in color, without requiring sunlight irradiation, and hence are devices that have rendered color changes possible regardless of weather, time, or the place of use. However, since a light source which emits light including ultraviolet rays is employed in those optically color-changing devices in order to cause photochromic compounds to change in color, there is a fear about influences thereof on the human body.